docs: def _get_config_files():
      """Get the possible configuration files accepted by oslo.config
  
      This also includes the deprecated ones
      """
      # default files
      conf_files = cfg.find_config_files(project='monasca',
                                         prog='monasca-persister')
      # deprecated config files (only used if standard config files are not there)
      if len(conf_files) == 0:
          old_conf_files = cfg.find_config_files(project='monasca',
                                                 prog='persister')
          if len(old_conf_files) > 0:
              LOG.warning('Found deprecated old location "{}" '
                          'of main configuration file'.format(old_conf_files))
              conf_files += old_conf_files
      return conf_files